Factor structure and convergent validity of the Derriford Appearance Scale-24 using standard scoring versus treating 'not applicable' responses as missing data: a Scleroderma Patient-centered Intervention Network (SPIN) cohort study.

Autor:	Merz EL; Department of Psychology, California State University, Dominguez Hills, Carson, California, USA., Kwakkenbos L; Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec, Canada.; Department of Psychiatry, McGill University, Montreal, Quebec, Canada.; Behavioral Science Institute, Clinical Psychology, Radboud University, Nijmegen, The Netherlands., Carrier ME; Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec, Canada., Gholizadeh S; San Diego State University/University of California San Diego Joint Doctoral Program in Clinical Psychology, San Diego, California, USA., Mills SD; San Diego State University/University of California San Diego Joint Doctoral Program in Clinical Psychology, San Diego, California, USA., Fox RS; San Diego State University/University of California San Diego Joint Doctoral Program in Clinical Psychology, San Diego, California, USA.; Department of Medical Social Sciences, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA., Jewett LR; Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec, Canada.; Department of Educational and Counseling Psychology, McGill University, Montreal, Quebec, Canada., Williamson H; Centre for Appearance Research, Faculty of Health and Life Science, University of the West of England, Bristol, UK., Harcourt D; Centre for Appearance Research, Faculty of Health and Life Science, University of the West of England, Bristol, UK., Assassi S; Department of Internal Medicine, Division of Rheumatology, University of Texas McGovern Medical School, Houston, Texas, USA., Furst DE; Division of Rheumatology, Geffen School of Medicine at the University of California, Los Angeles, California, USA., Gottesman K; Scleroderma Foundation, Los Angeles, California, USA., Mayes MD; Department of Internal Medicine, Division of Rheumatology, University of Texas McGovern Medical School, Houston, Texas, USA., Moss TP; Centre for Appearance Research, Faculty of Health and Life Science, University of the West of England, Bristol, UK., Thombs BD; Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec, Canada.; Department of Psychiatry, McGill University, Montreal, Quebec, Canada.; Department of Educational and Counseling Psychology, McGill University, Montreal, Quebec, Canada.; Department of Epidemiology, Biostatistics, and Occupational Health, McGill University, Montreal, Quebec, Canada.; Department of Medicine, McGill University, Montreal, Quebec, Canada., Malcarne VL; San Diego State University/University of California San Diego Joint Doctoral Program in Clinical Psychology, San Diego, California, USA.; Department of Psychology, San Diego State University, San Diego, California, USA.
Jazyk:	angličtina
Zdroj:	BMJ open [BMJ Open] 2018 Mar 06; Vol. 8 (3), pp. e018641. Date of Electronic Publication: 2018 Mar 06.
DOI:	10.1136/bmjopen-2017-018641
Abstrakt:	Objective: Valid measures of appearance concern are needed in systemic sclerosis (SSc), a rare, disfiguring autoimmune disease. The Derriford Appearance Scale-24 (DAS-24) assesses appearance-related distress related to visible differences. There is uncertainty regarding its factor structure, possibly due to its scoring method. Design: Cross-sectional survey. Setting: Participants with SSc were recruited from 27 centres in Canada, the USA and the UK. Participants who self-identified as having visible differences were recruited from community and clinical settings in the UK. Participants: Two samples were analysed (n=950 participants with SSc; n=1265 participants with visible differences). Primary and Secondary Outcome Measures: The DAS-24 factor structure was evaluated using two scoring methods. Convergent validity was evaluated with measures of social interaction anxiety, depression, fear of negative evaluation, social discomfort and dissatisfaction with appearance. Results: When items marked by respondents as 'not applicable' were scored as 0, per standard DAS-24 scoring, a one-factor model fit poorly; when treated as missing data, the one-factor model fit well. Convergent validity analyses revealed strong correlations that were similar across scoring methods. Conclusions: Treating 'not applicable' responses as missing improved the measurement model, but did not substantively influence practical inferences that can be drawn from DAS-24 scores. Indications of item redundancy and poorly performing items suggest that the DAS-24 could be improved and potentially shortened. Competing Interests: Competing interests: The authors have read and understood the BMJ policy on declaration of interests and declare the following interests: the DAS-24 is commercially available from TPM. (© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)
Databáze:	MEDLINE
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